Hey Abigail, I read Tolle's book "A new earth". It has elements of "Power of Now" but steps further of how mankind may shift to a "higher level of consciousness". In this context, he pleads for a clean mind that might prevent anger, pain, hate, and everything which makes the world unhappy and hostile. Thinking in the past and future always brings you away from the moment and is (in Tolle's opinion) an ego reaction which is the root cause of disadvantage developments on earth. It was a recommendation by a friend and I really enjoyed to read it.

Have fun

Chapper